The present invention relates to an apparatus for reading DX bar codes and frame number bar codes which are printed along edges of photographic film.
DX bar codes representative of a film type (maker and film sensitivity) are printed in the form of a latent image on a side portion of a negative (e.g. 135 type) film, the DX bar codes being made visible upon development of the film. The DX bar code is constructed of a clock track used for reading timings. and a data track on which data are recorded. both tracks being printed in juxtaposed arrangement on the negative film. The DX bar code read with a bar code is sensor unit at the time of printing or at the time of inspecting the quality (color balance and density) of the frame image. The read-out film type data are used in calculating the exposure amount for printing.
It is also known to print a frame number bar code representative of a frame number along the lengthwise edge of a photographic film. The frame number bar code is used, e.g., for searching for a desired frame to obtain additional prints thereof and automatically setting that frame at the print stage of a printer, for recording a frame number on some area of the print to dispense with the comparison work between a print and the frame. and for other reasons known to those of ordinary skill in this field.
Printing both DX bar codes and frame number bar codes along the lengthwise edge of a photographic film requires the use of different types of bar codes to allow discrimination therebetween. Moreover it becomes necessary to use two bar code sensor units. dedicated to each of the two types of bar codes, and mounted on a film carrier at both the sides of a film passage. However, it becomes necessary to set the film on the film carrier in a predetermined direction with either the smallest frame number or the largest frame number at the start position. If a film is set in the wrong direction, neither the DX bar codes nor the frame number bar codes can be read correctly. Also, if a film is set upside down at the film carrier, the bar codes cannot be read correctly and a photograph printed from the rear side is produced, thus resulting in loss of material and work time.
A photographic film is liable to vibrations in the film feeding direction due to backlash in a film feeding mechanism. resulting in double reading of the same bar or space of a bar code. Apart from the above, even if a read error occurs for a DX bar code, the following same DX bar code printed at equal intervals on film may be read thus posing no problem. However, only one frame number bar code is present for each particular frame, so that if the bar code sensor unit erroneously reads the frame number, the erroneously read frame number, when set at the print stage, cannot be identified.